U.S. patent application number 10/525288 was filed with the patent office on 2005-09-15 for process and system for laser crystallization processing of film regions on a substrate to provide substantial uniformity, and a structure of such film regions.
Invention is credited to Im, James S..
Application Number | 20050202654 10/525288 |
Document ID | / |
Family ID | 31888393 |
Filed Date | 2005-09-15 |
United States Patent
Application |
20050202654 |
Kind Code |
A1 |
Im, James S. |
September 15, 2005 |
Process and system for laser crystallization processing of film
regions on a substrate to provide substantial uniformity, and a
structure of such film regions
Abstract
A process and system for processing a thin film sample (e.g., a
semiconductor thin film), as well as the thin film structure are
provided. In particular, a beam generator can be controlled to emit
at least one beam pulse. With this beam pulse, at least one portion
of the film sample is irradiated with sufficient intensity to fully
melt such section of the sample throughout its thickness, and the
beam pulse having a predetermined shape. This portion of the film
sample is allowed to resolidify, and the re-solidified at least one
portion is composed of a first area and a second area. Upon the
re-solidification thereof, the first area includes large grains,
and the second area has a region formed through nucleation. The
first area surrounds the second area and has a grain structure
which is different from a grain structure of the second area. The
second area is configured to facilitate thereon an active region of
an electronic device.
Inventors: |
Im, James S.; (New York,
NY) |
Correspondence
Address: |
BAKER & BOTTS
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
|
Family ID: |
31888393 |
Appl. No.: |
10/525288 |
Filed: |
February 16, 2005 |
PCT Filed: |
August 19, 2003 |
PCT NO: |
PCT/US03/25946 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60405084 |
Aug 19, 2002 |
|
|
|
Current U.S.
Class: |
438/487 ;
117/206; 117/219; 257/49; 438/160; 438/166 |
Current CPC
Class: |
H01L 29/66757 20130101;
H01L 21/02686 20130101; Y10T 117/1024 20150115; H01L 29/78675
20130101; H01L 21/2026 20130101; H01L 21/02532 20130101; H01L
27/1296 20130101; Y10T 117/1076 20150115; H01L 27/1285
20130101 |
Class at
Publication: |
438/487 ;
438/160; 438/166; 117/206; 117/219; 257/049 |
International
Class: |
H01L 021/428; C30B
035/00 |
Goverment Interests
[0002] The U.S. Government may have certain rights in this
invention pursuant to the terms of the Defense Advanced Research
Project Agency award number N66001-98-1-8913.
Claims
What is claimed is:
1. A method for processing a thin film sample, comprising the steps
of: (a) controlling a beam generator to emit at least one beam
pulse; (b) with the at least one beam pulse, irradiating at least
one portion of the film sample with sufficient intensity to fully
melt the at least one section of the sample throughout its
thickness; and (c) allowing the at least one portion of the film
sample to re-solidify, the re-solidified at least one portion being
composed of a first area and a second area, wherein, upon the
re-solidification thereof, the first area includes large grains,
and the second area has a small-grained region formed through
nucleation, wherein the first area surrounds the second area and
has a grain structure which is different from a grain structure of
the second area, and wherein the second area is configured to
facilitate thereon an active region of an electronic device.
2. The method according to claim 1, wherein the first area has a
first border and a second border which is provided opposite and
parallel to the first border of the first area, wherein the second
area has a third border and a fourth border which is provided
opposite and parallel to the third border of the second area, and
wherein a distance between the first border and the second border
is smaller than a distance between the third border and the fourth
border.
3. The method according to claim 2, wherein the second area
corresponds to at least one pixel.
4. The method according to claim 1, wherein the second area has a
cross-section for facilitating thereon all portions of the
electronic device.
5. The method according to claim 1, wherein a size and a position
of the first area with respect to the second area are provided such
that the first area provides either no effect or a negligible
effect on a performance of the electronic device.
6. The method according to claim 1, further comprising the steps
of: (d) translating the thin film sample for a predetermined
distance; (e) with a further beam pulse, irradiating a further
portion of the film sample, wherein the further portion is provided
at a distance from the at least one portion that substantially
corresponds to the predetermined distance; and (f) allowing the
further portion of the film sample to re-solidify, the
re-solidified at least one portion being composed of a third area
and a fourth area, wherein the third area surrounds the fourth
area, and wherein at least one section of the third area at least
partially overlaps at least one section of the first area, and
wherein, upon the re-solidification thereof, the third area has
laterally grown grains, and the fourth area has a nucleated
region.
7. The method according to claim 6, wherein the fourth area is
composed of edges which are provided away from edges of the second
area.
8. The method according to claim 6, wherein the fourth area is
composed of edges which approximately border edges of the second
area, and wherein the edges of the fourth area do not extend into
any section of the first area.
9. The method according to claim 6, wherein the at least one beam
pulse has a fluence which is substantially the same as a fluence of
the further beam pulse.
10. The method according to claim 6, wherein the at least one beam
pulse has a fluence which is different from a fluence of the
further beam pulse.
11. The method according to claim 1, further comprising the steps
of: (g) translating the thin film sample for a predetermined
distance; and (h) irradiating a further portion of the film sample
using at least one beam pulse, wherein the frther portion is
provided at a distance from the at least one portion that
substantially corresponds to the predetermined distance, and
wherein steps (d) and (e) are provided to control a width of the
first area.
12. The method according to claim 1, wherein the film sample is one
of a pre-patterned silicon thin film sample and a continuous
silicon thin film sample.
13. The method according to claim 1, wherein the electronic device
is a thin film transistor.
14. The method according to claim 1, further comprising the steps
of: (i) translating the thin film sample for a predetermined
distance; (j) irradiating a further portion of the film sample
using at least one beam pulse, wherein the further portion is
provided at a distance from the at least one portion that
substantially corresponds to the predetermined distance; and (k)
repeating steps (i) and (j) for additional portions of the film
sample without stopping the translation of the film sample after
the completion of the repeated step (j).
15. The method according to claim 14, wherein step (i) delivers the
film sample to a first relative pre-calculated position of the
further portion of the film sample to be irradiated, and wherein,
after step (k), the film sample is provided at a second relative
pre-calculated position whose distance is different from the
predetermined distance.
16. The method according to claim 1, further comprising the steps
of: (l) translating the thin film sample for a predetermined
distance; (m) stopping the translation of the film sample, and
allowing vibrations of the film sample to settle; and (n) after
step (m), irradiating a further portion of the thin film using at
least one beam pulse, wherein the further portion is provided at a
distance from the at least one portion that substantially
corresponds to the predetermined distance.
17. The method according to claim 1, further comprising the steps
of: (o) after step (c), irradiating the at least one portion of the
film sample with a further beam pulse; and (p) after step (o),
allowing the at least one portion of the film sample to
re-solidify.
18. The method according to claim 17, wherein a fluence of the at
least one beam pulse is different from a fluence of the further
beam pulse.
19. The method according to claim 18, wherein the fluence of the
further beam pulse is less than the fluence of the at least one
beam pulse.
20. The method according to claim 1, further comprising the step
of: (a) after step (c), determining a location of the first area so
as to avoid a placement of the active region of the electronic
device thereon.
21. The method according to claim 1, wherein the at least one beam
pulse includes a plurality of beamlets, and wherein the first and
second areas are irradiated by the beamlets.
22. The method according to claim 1, wherein the film sample is one
of a silicon thin film sample and a metal thin film sample.
23. The method according to claim 1, wherein the thin film sample
is composed of at least one of silicon, germanium, and a compound
of silicon germanium.
24. The method according to claim 1, wherein the thin film has a
thickness approximately between 100 .ANG. and 10,000 .ANG..
25. The method according to claim 1, further comprising the step
of: (r) before step (b), masking portions of the at least one beam
pulse to produce at least one masked beam pulse, wherein the at
least one masked beam pulse is used to irradiate the at least one
portion of the film sample in step (b).
26. The method according to claim 1, wherein the large grains
provided in the first area are laterally-grown grains.
27. The method according to claim 26, wherein the laterally-grown
grains of the first area are equiaxed grains.
28. A method for processing a thin film sample, comprising the
steps of: (a) controlling a beam generator to emit at least one
beam pulse; (b) with the at least one beam pulse, irradiating at
least one portion of the film sample with an intensity that is
sufficient to fully melt at least one section of the film sample
throughout its thickness, the at least one beam pulse having a
predetermined shape; (c) allowing the at least one portion of the
film sample to re-solidify, the re-solidified at least one portion
being composed of a first area and a second area, wherein the first
area surrounds the second area, and wherein, upon the
re-solidification thereof, the first area has large grains, and the
second area has a small-grained region formed through nucleation;
(d) translating the thin film sample for a predetermined distance;
and (e) irradiating a further portion of the thin film using a
further beam pulse, wherein the further portion is provided at a
distance from the at least one portion that substantially
corresponds to the predetermined distance, wherein steps (b) though
(e) are provided to control a width of the first area, and wherein
the second area has a cross-section to allow an active region of an
electronic device to be facilitated thereon.
29. The method according to claim 28, wherein the second area
corresponds to at least one pixel.
30. The method according to claim 28, wherein the first area has a
first border and a second border which is provided opposite and
parallel to the first border of the first area, wherein the second
area has a third border and a fourth border which is provided
opposite and parallel to the third border of the second area, and
wherein a distance between the first border and the second border
is smaller than a distance between the third border and the fourth
border.
31. The method according to claim 28, wherein the second area has a
cross-section for facilitating thereon all portions of the
electronic device.
32. The method according to claim 28, wherein a size and a position
of the first area with respect to the second area are provided such
that the first area provides either no effect or a negligible
effect on a performance of the electronic device.
33. The method according to claim 28, further comprising the steps
of: (f) after step (e), allowing the further portion of the film
sample to re-solidify, the re-solidified at least one portion being
composed of a third area and a fourth area, wherein the third area
surrounds the fourth area, and wherein at least one section of the
third area at least partially overlaps at least one section of the
first area, and wherein, upon the re-solidification thereof, the
third area has laterally grown grains, and the fourth area has a
nucleated region.
34. The method according to claim 33, wherein the fourth area is
composed of edges which are provided away from edges of the second
area.
35. The method according to claim 33, wherein the fourth area is
composed of edges which approximately border edges of the second
area, and wherein the edges of the fourth area do not extend into
any section of the first area.
36. The method according to claim 28, wherein the at least one beam
pulse has a fluence which is substantially the same as a fluence of
the further beam pulse.
37. The method according to claim 28, wherein the at least one beam
pulse has a fluence which is different from a fluence of the
further beam pulse.
38. The method according to claim 28, wherein the film sample is
one of a pre-patterned silicon thin film sample and a continuous
silicon thin film sample.
39. The method according to claim 28, wherein the electronic device
is a thin film transistor.
40. The method according to claim 28, further comprising the steps
of: (g) repeating steps (d) and (e) on additional portions of the
film sample without stopping the translation of the film
sample.
41. The method according to claim 40, wherein step (d) delivers the
film sample to a first relative pre-calculated position of the
further portion of the film sample to be irradiated, and wherein,
after step (e), the film sample is provided at a second relative
pre-calculated position whose distance is different from the
predetermined distance.
42. The method according to claim 28, further comprising the steps
of: (h) after step (d), stopping the translation of the film
sample, and allowing vibrations of the film sample to settle; and
(i) after step (h), irradiating a further portion of the thin film
using at least one beam pulse, wherein the further portion is
provided at a distance from the at least one portion that
substantially corresponds to the predetermined distance.
43. The method according to claim 42, wherein a fluence of the at
least one beam pulse is different from a fluence of the further
beam pulse.
44. The method according to claim 43, wherein the fluence of the
further beam pulse is less than the fluence of the at least one
beam pulse.
45. The method according to claim 28, wherein the at least one beam
pulse includes a plurality of beamlets, and wherein the first and
second areas are irradiated by the beamlets.
46. The method according to claim 28, wherein the film sample is
one of a silicon thin film sample and a metal thin film sample.
47. The method according to claim 28, wherein the thin film sample
is composed of at least one of silicon, germanium, and a compound
of silicon germanium.
48. The method according to claim 28, wherein the thin film has a
thickness approximately between 100 .ANG. and 10,000 .ANG..
49. The method according to claim 28, further comprising the step
of: (j) before step (b), masking portions of the at least one beam
pulse to produce at least one masked beam pulse, wherein the at
least one masked beam pulse is used to irradiate the at least one
portion of the film sample in step (b).
50. The method according to claim 28, wherein the large grains
provided in the first area are laterally-grown grains.
51. The method according to claim 50, wherein the laterally-grown
grains of the first area are equaled grains.
52. A system for processing a thin film sample, comprising: a
processing arrangement which is configured to: (a) control a beam
generator to emit at least one beam pulse which is sufficient to
fully melt at least one section of the film sample throughout its
thickness, (b) control a translation stage such that at least one
portion of the film sample is irradiated with the at least one beam
pulse, the at least one beam pulse having a predetermined cross
section, wherein the at least one portion of the film sample is
allowed to re-solidify, the re-solidified at least one portion
being composed of a first area and a second area, wherein, upon the
re-solidification thereof, the first area has large grains, and the
second area has a small-grained region formed through nucleation,
wherein the first area surrounds the second area and has a grain
structure which is different from a grain structure of the second
area, and wherein the second area is configured to facilitate
thereon an active region of an electronic device.
53. The system according to claim 52, wherein the second area
corresponds to at least one pixel.
54. The system according to claim 52, wherein the first area has a
first border and a second border which is provided opposite and
parallel to the first border of the first area, wherein the second
area has a third border and a fourth border which is provided
opposite and parallel to the third border of the second area, and
wherein a distance between the first border and the second border
is smaller than a distance between the third border and the fourth
border.
55. The system according to claim 52, wherein the second area has a
cross-section for facilitating thereon all portions of the
electronic device.
56. The system according to claim 52, wherein a size and a position
of the first area with respect to the second area are provided such
that the first area provides either no effect or a negligible
effect on a performance of the electronic device.
57. The system according to claim 52, wherein the processing
arrangement is further configured to: (c) control the translation
stage to translate the thin film sample for a predetermined
distance, and (d) control the laser beam generator to irradiating a
further portion of the film sample with a further beam pulse, the
further portion being provided at a distance from the at least one
portion that substantially corresponds to the predetermined
distance, wherein the further portion of the film sample is allowed
to re-solidify, the re-solidified at least one portion being
composed of a third area and a fourth area, wherein the third area
surrounds the fourth area, and wherein at least one section of the
third area at least partially overlaps at least one section of the
first area, and wherein, upon the re-solidification thereof, the
third area has laterally grown grains, and the fourth area has a
nucleated region.
58. The system according to claim 57, wherein the fourth area is
composed of edges which are provided away from edges of the second
area.
59. The system according to claim 57, wherein the fourth area is
composed of edges which approximately border edges of the second
area, and wherein the edges of the fourth area do not extend into
any section of the first area.
60. The system according to claim 52, wherein the at least one beam
pulse has a fluence which is substantially the same as a fluence of
the further beam pulse.
61. The system according to claim 52, wherein the at least one beam
pulse has a fluence which is different from a fluence of the
further beam pulse.
62. The system according to claim 52, wherein the processing
arrangement is further configured to: (e) control the translation
stage to translate the thin film sample for a predetermined
distance, and (f) control the laser beam generator to irradiate a
further portion of the film sample using at least one beam pulse,
wherein the further portion is provided at a distance from the at
least one portion that substantially corresponds to the
predetermined distance, and wherein the processing arrangement
irradiates the at least one portion and allows the at least one
portion to re-solidify to control a width of the first area.
63. The system according to claim 52, wherein the film sample is
one of a pre-patterned silicon thin film sample and a continuous
silicon thin film sample.
64. The system according to claim 52, wherein the electronic device
is a thin film transistor.
65. The system according to claim 52, wherein the processing
arrangement is further configured to: (g) control the translation
stage to translate the thin film sample for a predetermined
distance, (h) control the laser beam generator to irradiate a
further portion of the film sample using at least one beam pulse,
wherein the further portion is provided at a distance from the at
least one portion that substantially corresponds to the
predetermined distance; and (i) repeat procedures (g) and (h) for
additional portions of the film sample without stopping the
translation of the film sample after the completion of the repeated
procedure (i).
66. The system according to claim 65, wherein the processing
arrangement performs procedure (g) to deliver the film sample to a
first relative pre-calculated position of the further portion of
the film sample to be irradiated, and wherein, after the processing
arrangement performs procedure (i), the film sample is provided at
a second relative pre-calculated position whose distance is
different from the predetermined distance.
67. The system according to claim 52, wherein the processing
arrangement is further configured to: (j) control the translation
stage to translate the thin film sample for a predetermined
distance, stop the translation of the film sample, and allow
vibrations of the film sample to settle, and (k) after procedure
(j), control the laser beam generator to irradiate a further
portion of the thin film using at least one beam pulse, wherein the
further portion is provided at a distance from the at least one
portion that substantially corresponds to the predetermined
distance.
68. The system according to claim 52, wherein the processing
arrangement is further configured to: (l) after procedure (b),
control the laser beam generator to irradiate the at least one
portion of the film sample with a further beam pulse, and (m) after
procedure (l), allow the at least one portion of the film sample to
re-solidify.
69. The system according to claim 58, wherein a fluence of the at
least one beam pulse is different from a fluence of the further
beam pulse.
70. The system according to claim 69, wherein the fluence of the
further beam pulse is less than the fluence of the at least one
beam pulse.
71. The system according to claim 52, wherein the at least one beam
pulse includes a plurality of beamlets, and wherein the first and
second areas are irradiated by the beamlets.
72. The system according to claim 52, wherein the film sample is
one of a silicon thin film sample and a metal thin film sample.
73. The system according to claim 52, wherein the thin film sample
is composed of at least one of silicon, germanium, and a compound
of silicon germanium.
74. The system according to claim 52, wherein the thin film has a
thickness approximately between 100 .ANG. and 10,000 .ANG..
75. The system according to claim 52, wherein the processing
arrangement is further configured to: (l) during procedure (b),
mask portions of the at least one beam pulse to produce at least
one masked beam pulse, wherein the at least one masked beam pulse
is used to irradiate the at least one portion of the film sample in
procedure (b).
76. The system according to claim 52, wherein the large grains
provided in the first area are laterally-grown grains.
77. The system according to claim 76, wherein the laterally-grown
grains of the first area are equiaxed grains.
78. A system for processing a thin film sample, comprising: a
processing arrangement which is configured to: (a) control a beam
generator to emit at least one beam pulse which has an intensity
which is sufficient to fully melt at least one section of the film
sample throughout its entire thiclness, (b) control a translation
stage such that at least one portion of the film sample is
irradiated with the at least one beam pulse, the at least one beam
pulse having a predetermined cross section, wherein the at least
one portion of the film sample is allowed to re-solidify, the
re-solidified at least one position being composed of a first area
and a second area, and wherein, upon the re-solidification thereof,
the first area has large grains, and the second area has a
small-grained region formed through nucleation, (c) control the
translation stage to translate the thin film sample for a
predetermined distance, and (d) control the laser beam generator to
irradiate a further portion of the thin film using a further beam
pulse, the further portion being provided at a distance from the at
least one portion that substantially corresponds to the
predetermined distance, wherein procedures (b) through (d) are
provided to control a width of the first area, and wherein a width
of the second area is configured to facilitate thereon an active
region of an electronic device.
79. The system according to claim 78, wherein the second area
corresponds to at least one pixel.
80. The system according to claim 78, wherein the first area has a
first border and a second border which is provided opposite and
parallel to the first border of the first area, wherein the second
area has a third border and a fourth border which is provided
opposite and parallel to the third border of the second area, and
wherein a distance between the first border and the second border
is smaller than a distance between the third border and the fourth
border.
81. The system according to claim 80, wherein, upon the
re-solidification of the film sample, a nucleated region is formed
in the second area.
82. The system according to claim 78, wherein the second area has a
cross-section for facilitating thereon all portions of the
electronic device.
83. The system according to claim 78, wherein a size and a position
of the first area with respect to the second area are provided such
that the first area provides either no effect or a negligible
effect on a performance of the electronic device.
84. The system according to claim 78, wherein the further portion
of the film sample is allowed to re-solidify, the re-solidified at
least one portion being composed of a third area and a fourth area,
and wherein the third area surrounds the fourth area, wherein at
least one section of the third area at least partially overlaps at
least one section of the first area, and wherein, upon the
re-solidification thereof, the third area has laterally grown
grains, and the fourth area has a nucleated region.
85. The system according to claim 84, wherein the fourth area is
composed of edges which are provided away from edges of the second
area.
86. The system according to claim 84, wherein the fourth area is
composed of edges which approximately border edges of the second
area, and wherein the edges of the fourth area do not extend into
any section of the first area.
87. The system according to claim 78, wherein the at least one beam
pulse has a fluence which is substantially the same as a fluence of
the further beam pulse.
88. The system according to claim 78, wherein the at least one beam
pulse has a fluence which is different from a fluence of the
further beam pulse.
89. The system according to claim 78, wherein the filhn sample is
one of a pre-patterned silicon thin film sample and a continuous
silicon thin film sample.
64. The system according to claim 78, wherein the electronic device
is a thin film transistor.
91. The system according to claim 78, wherein the processing
arrangement is further configured to: (e) repeat procedures (c) and
(d) on additional portions of the film sample without stopping the
translation of the film sample.
92. The system according to claim 89, wherein procedure (c)
delivers the film sample to a first relative pre-calculated
position of the further portion of the film sample to be
irradiated, and wherein, after procedure (d), the film sample is
provided at a second relative pre-calculated position whose
distance is different from the predetermined distance.
93. The system according to claim 78, wherein the processing
arrangement is furher configured to: (f) after procedure (e),
control the translation stage to stop the translation of the film
sample, and allow vibrations of the film sample to settle, and (g)
after procedure (f), control the laser beam generator to irradiate
a further portion of the thin film using at least one beam pulse,
wherein the further portion is provided at a distance from the at
least one portion that substantially corresponds to the
predetermined distance.
94. The system according to claim 93, wherein a fluence of the at
least one beam pulse is different from a fluence of the further
beam pulse.
95. The system according to claim 93, wherein the fluence of the
further beam pulse is less than the fluence of the at least one
beam pulse.
96. The system according to claim 78, wherein the at least one beam
pulse includes a plurality of beamlets, and wherein the first and
second areas are irradiated by the beamlets.
97. The system according to claim 78, wherein the film sample is
one of a silicon thin film sample and a metal thin film sample.
98. The system according to claim 78, wherein the thin film sample
is composed of at least one of silicon, germanium, and a compound
of silicon germanium.
99. The system according to claim 78, wherein the thin film has a
thickness approximately between 100 .ANG. and 10,000 .ANG..
100. The system according to claim 78, wherein the processing
arrangement is further configured to: (l) during procedure (b),
mask portions of the at least one beam pulse to produce at least
one masked beam pulse, wherein the at least one masked beam pulse
is used to irradiate the at least one portion of the film sample in
procedure (b).
101. The system according to claim 78, wherein the large grains
provided in the first area are laterally-grown grains.
102. The system according to claim 101, wherein the laterally-grown
grains of the first area are equiaxed grains.
103. A thin film sample, comprising: at least one section
irradiated by at least one beam pulse which fully melts the at
least one section of the sample throughout its thickness, wherein
the at least one portion of the film sample is re-solidified to
include a first area and a second area, wherein, upon the
re-solidification of the at least one section, the first area
includes large grains, and the second area includes a region formed
through nucleation, wherein the first area surrounds the second
area and has a grain structure which is different from a grain
structure of the second area, and wherein the second area is
configured to facilitate thereon an active region of an electronic
device.
104. A thin film sample, comprising: a first area having large
grains; and a second area being surrounded by the first area and
including a region formed through nucleation of at least one
section of the thin film in which the second area is situated,
wherein the first area has a grain structure which is different
from a grain structure of the second area, and wherein the second
area is configured to facilitate thereon an active region of an
electronic device.
Description
RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional
Application No. 60/405,084, which was filed on Aug. 19, 2002, and
is incorporated by reference.
FIELD OF THE INVENTION
[0003] The present invention relates to techniques for processing
of films, and more particularly to techniques for processing films
to obtain a substantially uniform grain region for placing at least
an active region of a thin-film transistor ("TFT") therein.
BACKGROUND OF THE INVENTION
[0004] Semiconductor films, such as silicon films, are known to be
used for providing pixels for liquid crystal display devices. Such
films have previously been processed (i.e., irradiated by an
excimer laser and then crystallized) via excimer laser annealing
("ELA") methods. However, the semiconductor films processed using
such known ELA methods often suffer from microstructural
non-uniformities, which manifest themselves in availing a
non-uniform performance of thin-film transistor ("TFT") devices
fabricated on such films. The non-uniformity generally stems from
the intrinsic pulse-to-pulse variations in the output energy of the
excimer lasers irradiating the semiconductor films. The
above-described non-uniformity could manifest itself in, for
example, a noticeable difference in a brightness level of the
pixels in one area of the display as compared to the brightness in
other areas thereof.
[0005] Significant effort has gone into the refinement of
"conventional" ELA (also known as line-beam ELA) processes in the
attempt to reduce or eliminate the non-uniformity. For example,
U.S. Pat. No. 5,766,989 issued to Maegawa et al., the entire
disclosure of which is incorporated herein in its entirety by
reference, describes the ELA methods for forming polycrystalline
thin film and a method for fabricating a thin-film transistor. This
publication attempts to address the problem of non-uniformity of
characteristics across the substrate, and provide certain options
for apparently suppressing such non-uniformities.
[0006] However, the details of the beam-shaping approach used in
conventional ELA methods make it extremely difficult to reduce the
non-uniformities in the semiconductor films. This is especially
because the energy fluence described above may be different for
each beam pulse, and thus non-uniformity may be introduced into
sections of the semiconductor thin film upon irradiation,
solidification and crystallization.
[0007] Techniques for fabricating large grained single crystal or
polycrystalline silicon thin films using sequential lateral
solidification are known in the art. For example, in U.S. Pat. No.
6,322,625 issued to Im and U.S. patent application Ser. No.
09/390,537, the entire disclosures of which are incorporated herein
by reference, and which is assigned to the common assignee of the
present application, particularly advantageous apparatus and
methods for growing large grained polycrystalline or single crystal
silicon structures using energy-controllable laser pulses and
small-scale translation of a silicon sample to implement sequential
lateral solidification have been described. In these patent
documents, it has been discussed in great detail that at least
portions of the semiconductor film on a substrate are irradiated
with a suitable radiation pulse to completely melt such portions of
the film throughout their thickness. In this manner, when the
molten semiconductor material solidifies, a crystalline structure
grows into the solidifying portions from selected areas of the
semiconductor film which did not undergo a complete melting. This
publication mentions that the small grain growth in regions in
which nucleation may occur. As is known in the art, such nucleation
generates small grained material in the area of the nucleation.
[0008] As was previously known to those having ordinary skill in
the art of a sequential lateral solidification ("SLS") as described
in U.S. Pat. No. 6,322,625, which utilizes the irradiation of a
particular area using beam pulses whose cross-sectional areas are
large, it is possible for the nucleation to occur in such areas
before a lateral crystal growth is effectuated in such area. This
was generally thought to be undesirable, and thus the placement of
the TFT devices within these area was avoided.
[0009] While certain TFT devices do not require a high performance
level, they require good uniformity in certain applications.
Accordingly, it may be preferable to generate substrates which
include the semiconductor films that allow uniform small-grained
material to be produced therein, without the need for a multiple
irradiation of the same area on the semiconductor thin film.
SUMMARY OF THE INVENTION
[0010] One of the objects of the present invention is to provide an
improved process and system to which can produce generally uniform
areas on the substrate films such that the TFT devices can be
situated in such areas. Another object of the present invention is
to allow such areas to be nucleated (based on the threshold
behavior of the beam pulse), and then solidified, such that upon
re-solidification, the nucleated area becomes a region with uniform
small grained material. It is also another object of the present
invention to increase the speed to process the semiconductor films
for their use with the liquid crystal displays or organic light
emitting diode displays. It is still another object of the present
invention to allow each irradiated area of the semiconductor thin
film to be irradiated once, without the need to re-irradiate a
substantial portion thereof, while still providing a good uniform
material therein.
[0011] In accordance with at least some of these objectives as well
as others that will become apparent with reference to the following
specification, it has now been determined that the nucleated and
small grained material have an extremely good uniformity (e.g.,
uniform grains). It was also ascertained that the grain size in
such nucleated areas does not vary even in a significant manner if
the beam pulses melting these areas have fluctuating energy
densities. This is particularly the case when the beam's energy
density stays above the required threshold for fully melting these
areas throughout their thickness. For example, in the case of a
semiconductor film which has a thickness of approximately 0.1
.mu.m, the energy density of each beam pulse should be above 50
mJ/cm.sup.2. Further, the uniformity in the thin film was found to
be insensitive to a spatial non-uniformity of the beam incident on
the semiconductor film so long as the minimum intensity of the beam
is above the above-described threshold.
[0012] In one exemplary embodinent of the present invention, a
process and system for processing a semiconductor thin film sample
are provided. in particular, a beam generator can be controlled to
emit at least one beam pulse. With this beam pulse, at least one
portion of the film sample is irradiated with sufficient intensity
to fully melt such section of the sample throughout its thiclness.
Such beam pulse may have a predetermined shape. This portion of the
film sample is allowed to re-solidify, and the resolidified portion
is composed of a first area and a second area. Upon the
re-solidification thereof, the first area includes large grains,
and the second area has a small-grained region fonned through
nucleation. The first area surrounds the second area and has a
grain structure which is different from a grain structure of the
second area. The second area is configured to facilitate thereon an
active region of a thin-film transistor ("TFT").
[0013] In another exemplary embodiment of the present invention,
the first area has a first border and a second border which is
provided opposite and parallel to the first border of the first
area. Also, the second area has a third border and a fourth border
which is provided opposite and parallel to the third border of the
second area. A distance between the first border and the second
border is smaller than a distance between the third border and the
fourth border. The second area preferably corresponds to at least
one pixel. In addition, the second area may have a cross-section
for facilitating thereon all portions of the TFT. It is also
possible for a portion of the first area to contain thereon a small
section of the TFT. A size and a position of the first area with
respect to the second area can be provided such that there is no
effect or a negligible effect on a performance of the TFT by the
first area.
[0014] According to yet another embodiment of the present
invention, the thin film sample can be translated for a
predetermined distance. With a futher beam pulse, a further portion
of the film sample can be irradiated. The further portion is
provided at a distance from such portion that substantially
corresponds to the predetermined distance. This further portion of
the film sample is allowed to re-solidify, the re-solidified
portion being composed of a third area and a fourth area. In
addition, the third area can surround the fourth area, and at least
one section of the third area at least partially overlaps at least
one section of the first area. Further, upon the re-solidification
thereof, the third area has laterally grown grains, and the fourth
area has a nucleated region. The fourth area can also be composed
of edges which are provided away from edges of the second area.
Furthermore, the fourth area may be composed of edges which are
approximately border edges of the second area, and the edges of the
fourth area may not necessarily extend into any section of the
first area. The beam pulse may have a fluence which is
substantially the same as a fluence of the further beam pulse (or
different therefrom).
[0015] In still another embodiment of the present invention, the
thin film sample can be translated for a predetermined distance.
Then, a further portion of the film sample can be irradiated using
the beam pulse. The further portion is provided at a distance from
such portion that substantially corresponds to the predetermined
distance. The film sample may be a pre-patterned silicon thin film
sample or a continuous silicon thin film sample. In addition, the
thin film sample can be translated for a predetermined distance,
and a further portion of the film sample may be irradiated using at
least one beam pulse. The further portion is preferably provided at
a distance from this portion that substantially corresponds to the
predetermined distance. In addition, the film sample can be
delivered to a first relative pre-calculated position of the
further portion of the film sample to be irradiated. After such
delivery, the film sample may be provided at a second relative
precalculated position whose distance is different from the
predetermined distance.
[0016] According to further embodiment of the present invention,
the thin film sample can again be translated for a predetermined
distance. Then, the translation of the film sample may be stopped,
and vibrations of the film sample to allowed to settle. Thereafter,
a further portion of the thin film is irradiated using at least one
beam pulse, with the further portion being provided at a distance
from such portion that substantially corresponds to the
predetermined distance. Then, the portion of the film sample is
irradiated with a further beam pulse, and allowed to re-solidify. A
fluence of the beam pulse is different from a fluence of the
further beam pulse (e.g., less than the fluence of the beam
pulse).
[0017] According to still further embodiment of the present
invention, a location of the first area is determined so as to
avoid a placement of the active region of the TFT thereon. The beam
pulse preferably includes a plurality of beamlets, and the first
and second areas are irradiated by the beamlets. The semiconductor
thin film sample may be a silicon thin film sample, and possibly
composed of silicon, germanium or an alloy thereof. The
semiconductor thin film may have a thickness approximately between
100 .ANG. and 10,000 .ANG.. Portions of the beam pulse can be
masked to produce at least one masked beam pulse, such that the
masked beam pulse is used to irradiate the portion of the film
sample. The large grains provided in the first area may be
laterally-grown grains, and the laterally-grown grains of the first
area can be equiaxed grains.
[0018] According yet another embodiment of the present invention, a
semiconductor thin film sample is provided which has a first area
and a second area. The first area preferably has large grains
therein. The second area is surrounded by the first area and
includes a region formed through nucleation of at least one section
of the semiconductor thin film in which the second area is
situated. The structure of the grains of the first area is
different from a structure of the grains of the second area. The
second area is preferably configured to facilitate thereon an
active region of a thin-film transistor ("TFT").
[0019] The accompanying drawings, which are incorporated and
constitute part of this disclosure, illustrate a preferred
enbodiment of the invention and serve to explain the principles of
the invention.
BRIEF DESCRIPTIO OF THE DRAWINGS
[0020] FIG. 1A is a schematic block diagram of an exemplary
embodiment of an irradiation system according to the present
invention which irradiates particular areas of a semiconductor thin
film of a sample so that they nucleate and solidify to produce
uniform small grained regions;
[0021] FIG. 1B is an enlarged cross-sectional side view of the
sample which includes the semiconductor thin film;
[0022] FIG. 2 is a top exploded view of an exemplary embodiment of
the sample conceptually subdivided, and having a semiconductor thin
film thereon on which a process according to the present invention
is performed for the entire surface area a semiconductor thin film
using the exemplary system of FIG. 1A;
[0023] FIG. 3 is a top view of a first exemplary embodiment of a
mask according to the present invention which has a beam-blocking
area surrounding one open or transparent area, and which can be
used with the exemplary system of FIG. 1A to mask the beam pulses
generated by a laser beam source into a patterned beam pulse, such
that such masked beam pulses irradiate the particular areas on the
semiconductor film;
[0024] FIGS. 4A-4D are irradiations, by the radiation beam pulse
which is masked by the mask of FIG. 3, and then resolidifications
and crystallizations of the particular portions of the
semiconductor film provided on the sample for a first exemplary
conceptual column of the sample at various sequential stages of the
exemplary embodiment according to the process of the present
invention;
[0025] FIGS. 4E-4F are iradiations, by the radiation beam pulse
which is masked by the mask of FIG. 3, and then re-solidifications
and crystallizations of the particular portions of the
semiconductor film provided on the sample for a second exemplary
conceptual column of the sample at two exemplary sequential stages
of the processing according to the process of the present
invention;
[0026] FIG. 5A is a top view of a second exemplary embodiment of
the mask according to the present invention which has a
beam-bloeking area surrounding multiple small open or transparent
areas or slits, and which can be used with the exemplary system of
FIG. 1A to mask the beam pulses generated by a beam source into
patterned beamlets, such that such masked beamlet pulses irradiate
the particular areas on the semiconductor film;
[0027] FIG. 5B is an enlarged view of the beamlets of the second
embodiment of the mask illustrated in FIG. 5A;
[0028] FIGS. 6A-6D are irradiations, by the radiation beam pulse
intensity pattern which is masked by the mask of FIG. 5, and then
re-solidifications and crystallizations of the particular portions
of the semiconductor film provided on the sample for the first
exemplary conceptual column of the sample at various sequential
stages of the first exemplary embodiment of the exemplary
embodiment according to the process of the present invention;
[0029] FIG. 7 is an illustration of the semiconductor thin film
provided on the sample, and such thin film being irradiated by the
beam pulse having a cross-section that is patterned by a mask
having a beam-blocking area surrounding one long and narrow open or
transparent area, and which can be used with the exemplary system
of FIG. 1A;
[0030] FIG. 8A is an illustration of the two particular areas
irradiated, re-solidified and crystallized areas corresponding to
the areas of FIGS. 4D and 6D in which the entire TFT device is
situated in the small uniformed grained region formed through
nucleation;
[0031] FIG. 8B is an illustration of the two particular areas
irradiated, re-solidified and crystallized areas corresponding to
the areas of FIGS. 4D and 6D in which only the entire cross-section
of the active region of the TFT device is situated in the small
uniformed grained region formed through nucleation, while other
regions are provided over border areas between the crystallized
areas;
[0032] FIG. 9 is a flow diagram representing an exemplary
processing procedure of the present invention under at last partial
control of a computing arrangement of FIG. 1A using the exemplary
techniques of the present invention of FIGS. 4A-4F and 6A-6D;
and
[0033] FIG. 10 is a flow diagram representing another exemplary
processing procedure of the present invention under at least
partial control of a computing arrangement of FIG. 1A using the
exemplary techniques of the present invention of FIGS. 4A-4F and
6A-6D, and in which the beam source of FIG. 1A is triggered based
on the positions of the semiconductor film with respect to the
impingement of the beam.
DETAILED DESCRIPTION
[0034] It should be understood that various systems according to
the present invention can be utilized to generate, nucleate,
solidify and crystallize one or more areas on the semiconductor
(e.g., silicon) film which have uniform material therein such that
at least an active region of a thin-film transistor ("TFT") can be
placed in such areas. The exemplary embodiments of the systems and
process to achieve such areas, as well as of the resulting
crystallized semiconductor thin films shall be described in further
detail below. However, it should be understood that the present
invention is in no way limited to the exemplary embodiments of the
systems, processes and semiconductor thin films described
herein.
[0035] Certain systems for providing a continuous motion SLS are
described in U.S. patent application Ser. No. 09/526,585 (the "'585
application"), the entire disclosure of which is incorporated
herein by reference. Substantially solar systems according to the
exemplary embodiment of the present invention can be employed to
generate the nucleated, solidified and crystallized portions of the
semiconductor film described above on which it is possible to
situate the active regions of the TFT device. In particular, the
system according to the present invention is used on a sample 170
which has an amorphous silicon thin film thereof that is being
irradiated by irradiation beam pulses to promote the nucleation,
subsequent solidification and crystallization of the particular
areas of the semiconductor thin film. The exemplary system includes
a beam source 110 (e.g., a Lambda Physik model LPX-315I XeCl pulsed
excimer laser) emitting an irradiation beam (e.g., a laser beam), a
controllable beam energy density modulator 120 for modifying the
energy density of the laser beam, a MicroLas two plate variable
attenuator 130, beam steering mirrors 140, 143, 147, 160 and 162,
beam expanding and collimating lenses 141 and 142, a beam
homogenizer 144, a condenser lens 145, a field lens 148, a
projection mask 150 which may be mounted in a translating stage
(not shown), a 4.times.-6.times. eye piece 161, a controllable
shutter 152, a multi-element objective lens 163 for focusing a
radiation beam pulse 164 onto the sample 170 having the
semiconductor thin filn to be processed mounted on a sample
translation stage 180, a granite block optical bench 190 supported
on a vibration isolation and self-leveling system 191, 192, 193 and
194, and a computing arrangement 100 (e.g., a general purpose
computer executing a program according to the present invention or
a special-purpose computer) coupled to control the beam source 110,
the beam energy density modulator 120, the variable attenuator 130,
the shutter 152 and the sample translation stage 180.
[0036] The sample translation stage 180 is preferably controlled by
the computing arrangement 100 to effectuate translations of the
sample 170 in the planar X-Y directions, as well as in the Z
direction. In this manner, the computing arrangement 100 controls
the relative position of the sample 40 with respect to the
irradiation beam pulse 164. The repetition and the energy density
of the irradiation beam pulse 164 are also controlled by the
computer 100. It should be understood by those skilled in the art
that instead of the beam source 110 (e.g., the pulsed excimer
laser), the irradiation beam pulse can be generated by another
known source of short energy pulses suitable for completely melting
throughout their entire thickness selected areas of the
semiconductor (e.g., silicon) thin film of the sample 170 in the
manner described herein below. Such known source can be a pulsed
solid state laser, a chopped continuous wave laser, a pulsed
electron beam and a pulsed ion beam, etc. Typically, the radiation
beam pulses generated by the beam source 110 provide a beam
intensity in the range of 10 mJ/cm.sup.2 to 1 J/cm.sup.2, a pulse
duration (FWHM in the range of 10 to 103 nsec, and a pulse
repetition rate in the range of 10 Hz to 104 Hz.
[0037] While the computing arrangement 100, in the exemplary
embodiment of the system shown in FIG. 1A, controls translations of
the sample 170 via the sample stage 180 for carrying out the
processing of the semiconductor thin film of the sample 170
according to the present invention, the computing arrangement 100
may also be adapted to control the translations of the mask 150
and/or the beam source 110 mounted in an appropriate maskliaser
beam translation stage (not shown for the simplicity of the
depiction) to shift the intensity pattern of the irradiation beam
pulses 164, with respect to the semiconductor thin film of the
sample 170, along a controlled beam path. Another possible way to
shift the intensity pattern of the irradiation beam pulse is to
have the computer 100 control a beam steering mirror. The exemplary
system of FIG. 1 may be used to carry out the processing of the
silicon thin film of the sample 170 in the manner described below
in further detail. The mask 150 should be used by the exemplary
system of the present invention to well define the profile of the
resulting masked beam pulse 164 and to reduce the edge regions of
the portions of the semiconductor thin film when these portions are
irradiated by such masked beam pulse 164 and then crystallized.
[0038] As illustrated in FIG. 1B, the semiconductor thin film 175
of the sample 170 can be directly situated on e.g., a glass
substrate 172, and may be provided on one or more intermediate
layers 177 there between. The semiconductor thin film 175 can have
a thickness between 100 .ANG. and 10,000 .ANG. (1 .mu.m) so long as
at least certain necessary Us thereof can be completely melted
throughout their entire thickness. According to an exemplary
embodiment of the present invention, the semiconductor thin film
175 can be composed of silicon, germanium, silicon germanium
(SeGe), all of which preferably have low levels of impurities. It
is also possible to utilize other elements or semiconductor
materials for the semiconductor thin film 175. The intermediary
layer 177, which is situated immediately underneath the
semiconductor thin film 175, can be composed of silicon oxide
(SiO.sub.2), silicon nitride (Si.sub.3N.sub.4), and/or mixtures of
oxide, nitride or other materials that are suitable for promoting
nucleation and small grain growth within the designated areas of
the semiconductor thin film 175 of the sample 170. The temperature
of the glass substrate 172 can be between room temperature and
800.degree. C. Higher temperatures of the glass substrate 172 can
be accomplished by preheating the substrate 172 which would
effectively allow larger grains to be grown in the nucleated,
re-solidified, and then crystallized areas of the semiconductor
thin film 175 of the sample 170 due to the proximity of the glass
substrate 172 to the thin film 175.
[0039] FIG. 2 shows an enlarged view of an exemplary embodiment of
the semiconductor thin film 175 (e.g., an amorphous silicon thin
film) of the sample 170, and the relative translation paths of the
beam pulse 164 with respect to the locations on the sample 170.
This exemplary sample 170 has exemplary dimensions of 40 cm in the
Y direction by 30 cm in the X direction. The sample 170 can be
conceptually subdivided into a number of columns (e.g., a first
conceptual column 205, a second conceptual column 206, a third
conceptual column 207, etc.). The location/size of each conceptual
column may be stored in a storage device of the computing
arrangement 100, and utilized by the computing arrangement 100 for
later controlling the translation of the sample 170, and/or firing
of the beam by the beam source 110 on these locations of the
semiconductor thin film 175, or on other locations that are based
on the stored locations. Each of the columns 205, 206, 207, etc. is
dimensioned, e.g., 1/2 cm in the Y direction by 30 cm in the X
direction. Thus, if the sample 170 is sized 40 cm in the Y
direction, the sample 150 may be conceptually subdivided into
eighty (80) columns. The sample 170 may also be conceptually
subdivided into such columns having other dimensions (e.g., 1 cm by
30 cm columns, 2 cm by 30 cm columns, 2 cm by 30 cm columns, etc.).
In fact, there is absolutely no restrictions on the dimensions of
the conceptual columns of the sample 170 so long as the beam pulse
164 is capable of irradiating and completely melting certain areas
of the semiconductor thin film 175 in such columns so as to promote
nucleation, solidification, and small grain growth within such
areas for forming uniform areas on the film sample 175 to allow at
least the active region of the TFT device to be placed completely
therein without a concern of non-uniformity therein. The
location/dimension of each column, and the locations thereof, are
stored in the storage device of the computing arrangement 100, and
utilized by such computing arrangement 100 for controlling the
translation of the translation stage 180 with respect to the beam
pulse 164 and/or the firing of the beam 111 by the beam source
110.
[0040] The semiconductor thin film 175 can be irradiated by the
beam pulse 164 which is patterned using the mask 150 according to a
first exemplary embodiment of the present invention as shown in
FIG. 3. The first exemplary mask 150 is sized such that its
cross-sectional area is larger than that of the cross-sectional
area of the beam pulse 164. In this manner, the mask 150 can
pattern the pulsed beam to have a shape and profile directed by the
open or transparent regions of the mask 150. In this exemplary
embodiment, the mask 150 includes a beam-blocldng section 155 and
an open or transparent section 157. The beam-blocking section 155
prevents those areas of the pulsed beam impinging such section 155
from being irradiated there-through, thus preventing the further
entering the optics of the exemplary system of the present
invention shown in FIG. 1A to irradiate the corresponding areas of
the semiconductor thin film 175 provided on the sample 170. In
contrast, the open or transparent section 157 allows the portion of
the beam pulse 164 whose cross-section corresponds to that of the
section 157 to enter the optics of the system according to the
present invention, and irradiate the corresponding areas of the
semiconductor thin filn 175. In this manner, the mask 150 is
capable of pattering the beam pulse 164 so as to impinge the
semiconductor thin film 175 of the sample 170 at predetermined
portions thereof as shall be described in further detail below.
[0041] A first exemplary embodiment of the process according to the
present invention shall now be described with reference to the
irradiation of the semiconductor thin film 175 of the sample 170 as
illustrated in FIGS. 4A-4F. In this exemplary process of the
present invention, the beam 111 is shaped by the exemplary mask 150
of FIG. 3, and the exemplary irradiation and/or impingement of the
semiconductor thin film 175 of the sample 170 is shown in FIG. 2.
For example, the sample 170 may be translated with respect to the
beam pulse 164, either by moving the mask 150 or the sample
translation stage 180, in order to irradiate selective areas of the
semiconductor thin film 175 of the sample 170. For the purposes of
the foregoing, the length and width of the laser beam 149 may be
greater tham 1 cm in the X-direction by 1/2 cm in the Y-direction
(e.g., a rectangular shape) so that it can be shaped by the mask
150 of FIG. 3. However, it should be understood the pulsed laser
beam 149 is not limited to such shape and size. Indeed, other
shapes and/or sizes of the laser beam 149 are, of course,
achievable as is known to those having ordinary skill in the art
(e.g., shapes of a square, triangle, circle, etc.).
[0042] After the sample 170 is conceptually subdivided into columns
205, 206, 207, etc., a pulsed laser beam 111 is activated (by
actuating the beam source 110 using the computing device 100 or by
opening the shutter 130), and produces the pulsed laser beamlets
164 which impinges on a first location 220 which is away from the
semiconductor thin film 175. Then, the sample 170 is translated and
accelerated in the forward X direction under the control of the
computing arrangement 100 to reach a predetermined velocity with
respect to the fixed position beamlets in a first beam path
225.
[0043] In one exemplary variation of the process of the present
invention, the pulsed beamlets 164 can reach a first edge 210' of
the sample 170 preferably when the velocity of the movement of the
sample 170 with respect to the pulsed laser beam 149 reaches the
predetermined velocity. Then, the sample 170 is continuously (i.e.,
without stopping) translated in the -X direction at the predet ed
velocity so that the pulsed beamlets 164 continue irradiating
successive portions of the sample 170 for an entire length of a
second beam path 230.
[0044] After passing the first edge 210', the beam pulse 164
impinges and irradiates a first area 310 of the semiconductor thin
film 175, preferably with enough intensity to completely melt such
area throughout its thickness, as illustrated in FIG. 4A. Then, as
shown in FIG. 4B, this first area 310 is allowed to solidify and
crystallize, thereby forming two regions therein--a first
small-grained region 315 and a first laterally-grown region 318.
The first small-grained region 315 is formed after the nucleation
of the large section within the first area 310. The dimensions of
this region 315 are slightly smaller that the dimensions of the
beam pulse 164 irradiating the first area 310, with the first
small-grained region 315 being surrounded by the first
laterally-grown region 318 (the details of which are described
herein below).
[0045] The first laterally-grown region 318 is formed by laterally
growing the grains from the borders between the unmelted portions
of the semiconductor thin film 175 and the first melted area 310.
The grains in the first laterally-grown region 318 grown from these
borders toward the center of the first melted area for a
predetermined distance, to reach the first small- ed region 315 and
form a border there between. This predetermined distance is
controlled by the rate of re-solidification of the first melted
area 310. For example, the predetermined distance can be between 1
.mu.m and 5 .mu.m. Therefore, the first laterally-grown region 318
is significantly smaller that the first small-grained region 315
which it surrounds. Generally, the grains of the region 315 are
smaller than he grains of the region 318. However, the
small-grained material in the first small-grained region 315
provides a good uniformity for the placement of the TFT devices,
and at least the active regions thereof, in such uniform
small-grained region. For the purposes of the present invention, it
is undesirable to position the active regions of the TFT devices on
such small-grained regions.
[0046] Thereafter, as shown in FIG. 4C, the sample 170 is continued
to be translated (or the mask 150 is configured to be adjusted)
such that the beam pulse 164 irradiates and completely melts
(throughout its thickness) a second area 320 of the semiconductor
thin film 175. This second area 320 which can be a subsequent area
immediately following the first area 320 in the first conceptual
column 205 along the +X direction. Similarly to the first area 310,
the second area 320 re-solidifies and crystallizes into a second
small-gined region 325 and a second laterally-grown region 328,
which correspond to the characteristics and dimensions of the first
small-grained region 315 and the first laterally-grown region 318,
respectively. If, during the irradiation of the second area 320,
the beam pulse 164 slightly overlaps the first laterally-grown
region 318, then upon re-solidification, the grains in this region
318 seed and laterally grow a portion of the completed melted
second area 320 which is immediately adjacent to the first
laterally-grown region 318. In this manner, the adjacent section of
the second laterally-grown region 328 is seeded by the first
laterally-grown region 318 to laterally grow grams therefrom. The
resultant crystallized second area 320 is illustrated in FIG. 4D.
It is also within the scope of the present invention for the second
area 320 to be provided at a distance from the crystallized first
area 310. Accordingly, the sections of the second laterally-grown
region 328 which is situated closest to the crystallized first
laterally-grown region 318 is seeded by the grains from an
un-irradiated section between the first area 310 and the second
area.
[0047] The translation and irradiation of the first conceptual
column 205 of the semiconductor thin film 175 continues until all
areas 310, 320, . . . , 380, 390 (and their respective
small-grained regions 315, 325, . . . , 385, 395 and
laterally-grown regions 318, 328, . . . , 388, 398) in this first
conceptual column 205 is continued until the pulsed beamlets 164
reach a second edge 210" of the sample 170, as illustrated in FIG.
4E. The crystallization of the areas 310, 320, . . . , 380, 390
along the first conceptual column 205 is performed in a
substantially repetitive manner. When the beam pulse 164 passes the
second edge 210", the translation of the sample 170 may be slowed
with respect to the beam pulse 164 (in a third beam path 235) to
reach a second location 240 (FIG. 2). It should be noted that it is
not necessary to shut down the pulsed beam 111 after the beam pulse
164 has crossed the second edge 210" of the sample 170 because it
is no longer iradiating the sample 170.
[0048] While being away from the sample 170 and the second edge
210", the sample is translated in a -Y direction to a third
location 247 via a fourth beam path 245 so as to be able to
irradiate the sections of the semiconductor thin film 175 along the
second conceptual column 206. Then, the sample 170 is allowed to
settle at that location 247 to allow any vibrations of the sample
170 that may have occurred when the sample 170 was translated to
the third location 247 to cease. Indeed, for the sample 170 to
reach the second conceptual column 206, it is translated
approximately 1/2 cm for the columns having a width (in the -Y
direction) of 1/2 cm. The sample 170 is then accelerated to the
predetermined velocity via a fourth beam path 250 in the -X
direction so that the impingement of the semiconductor thin film
175 by the beam pulse 164 reaches, and then bypasses the second
edge 210".
[0049] Thereafter, the sample 170 is translated along a fifth beam
path 255, and the exemplary process described above with respect to
the irradiation of the first column 205 may then be repeated for
the second conceptual column 206 to irradiate further areas 410,
420, and their respective small-grained regions 415, 425 and
laterally-grown regions 418, 428 while translating the sample in
the +X direction. In this manner, all conceptual columns of the
sample 170 can be properly irradiated. Again, when the beam pulse
164 reaches the first edge 210', the translation of the sample 170
is decelerated along a sixth beam path 260 to reach a fourth
location 265. At that point, the sample 170 is translated in the -Y
direction along the seven beam path 270 for the beam pulse to be
outside the periphery of the sample 170 to reach fifth location
272, and the translation of the sample 170 is allowed to be stopped
so as to remove any vibrations from the sample 170. Thereafter, the
sample 170 is accelerated along the eighth beam path 275 in the -X
direction so that the beam pulse 164 reaches and passes the first
edge 210' of the sample 170, and the beam pulse 164 irradiates and
completely melts certain areas in the third conceptual column 207
so that they can crystallize in substantially the same manner as
described above for the areas 310, 320, . . . , 380, 390 of the
first conceptual column 205 and the areas 410, 420, . . . of the
second conceptual column 206.
[0050] This procedure may be repeated for all conceptual columns of
the semiconductor thin film 175, for selective columns of
particular sections of the thin film 175 which are not necessarily
conceptually subdivided into columns. In addition, it is possible
for the computing arrangement 100 to control the firing of the beam
111 by the beam source 110 based on the predefined location stored
in the storage device of the computing arrangement 100 (e.g.,
instead of irradiating the semiconductor thin film 175 by setting
predetermined pulse durations). For example, the computing
arrangement 100 can control the beams source 110 to generate the
beam 111 and irradiate only at the predetermined locations of
certain areas of the thin film 175 with its corresponding beam
pulse 164, such that these locations are stored and used by the
computing arrangement 100 to initiate the firing of the beam 111
which results in the irradiation by the beam pulse only when the
sample 170 is translated to situate those areas directly in the
path of the beam pulse 164. The beam source 110 can be fired via
the computing arrangement 100 based on the coordinates of the
location in the X direction.
[0051] In addition, it is possible to translate the sample 170 in a
marmer which is not necessary continuous, when the path of the
irradiation of the beam pulse 164 points to the areas on the
semiconductor thin film 175 to be melted and crystallized. Thus, it
is possible for the translation of the sample 170 to be stopped in
the middle of the sample 170, with the area in the middle being
irradiated, completely melted, and then re-solidified and
crystallized. Thereafter, the sample 170 can be moved so that
another section of the semiconductor thin film 175 is arranged in
the path of the beam pulse 164, such that the translation of the
sample is then stopped again and the particular section is
irradiated and completely melted in accordance with the exemplary
embodiment of the process described in great detail above, as well
as the embodiments of the process which shall be descnbed
below.
[0052] According to the present invention, any mask described and
shown herein and those described and illustrated in the '535
application may be used for the process and system according to the
present invention. For example, instead of using the mask shown in
FIG. 3 which allows the semiconductor thin film 175 to be
flood-irradiated, a second exemplary embodiment of the mask 150'
illustrated in FIG. 5A can be utilized. In contrast to the mask 150
of FIG. 3 which has a single open or transparent region 157, the
mask 150' has multiple open or transparent regions 450 which are
separated from one another by beam-blocking regions 455. The open
or trarent regions 450 of the mask 150' can also be referred to as
"slits." These slits permit small beam pulses (or beamlets) to
irradiate there-through and completely melt the areas of the
semiconductor thin film 175 that they impinge. An enlarged
illustration of one of the slits 450 is provided in FIG. 5B, which
shows that the dimensions of the slits 450 can be 0.5 .mu.m by 0.5
.mu.m. It should be clearly understood that other dimensions of the
slits are possible, and are within the scope of the present
invention. For example, the slits can have a rectangular shape, a
circular shape, a triangular shape, a chevron shape, a diamond
shape, etc.
[0053] FIGS. 6A-6D show an exemplary progression of a second
embodiment of the process according to the present invention in
which a plurality of successive areas along the first conceptual
column 205 of the semiconductor thin film 175 is irradiated by the
beam pulse 164 (comprised of beamlets) which is shaped by the mask
150' of FIG. 5A. The translation of the sample 170 with sect to the
impingement thereof by the beam pulse 164 is substantially the same
as the translation described above with reference to FIGS. 4A-4F.
The difference between the irradiation of the areas 310, 320, . . .
, 380, 390, 410, 420 by the beam pulse 164 shaped by the mask 150
of FIG. 3 and the areas 460, 470 by the beam pulse 164 shaped by
the mask 150' is that substantially the entire areas 310, 320, . .
. , 380, 390, 410, 420 are irradiated and completely melted, as
opposed to only certain small portions 462 of the areas 460, 470
are irradiated and completely melted throughout their entire
thickness.
[0054] Similarly to the area 310 in FIG. 4A, the portions 462 of
the area 460 are irradiated and completely melted as illustrated in
FIG. 6A. Thereafter, the portions 462 are re-solidified to form the
small-grained regions 465 (due to nucleation), and the laterally
grown regions 468 as shown in FIG. 4B. Similarly to the first
small-grained regions 315, the small-grained regions 465 of the
respective portions 462 have small grain uniform materials therein,
and are sized such that at least an active region of the TFT device
(and possible the entire TFT device) can be placed within each such
region 465. The small grain uniform material of the region 465 is
formed due to the nucleation and re-solidification of this region.
As shown in FIG. 6C, upon the translation of the sample 170 in the
-X direction, portions 472 of the area 470 are irradiated and
completely melted in a substantially the same manner as the
portions 462. In such manner, the small-grained regions 475 and the
laterally-grown regions 478 of the area 470 are formed.
[0055] In addition, it is possible to utilize a third embodiment of
a mask 150" according to the present invention as shown in FIG. 7
which has a long and narrow open or transparent region 490 so as to
pattern and shape the beam 149 into the beam pulse 164. For
example, the length of the region 490 can be 0.5 cm and the width
thereof may be 0.1 mm. In this manner, each conceptual column of
the sample 170 illustrated in FIG. 2 can be irradiated by the beam
pulse 164 shaped by this mask 150". In addition, it may be possible
for the length of the region 490 to be 30 cm. Thus, instead of
subdividing the semiconductor thin film 175 into a number of
conceptual columns, and irradiating each column separately, it is
possible to irradiate and completely melt selected portions of the
semiconductor thin film 175 by translating the sample 170 in the -Y
direction from one edge of the sample 170 to the opposite edge
thereof. It is important that the small-grained uniform regions be
formed using such processing technique such that it would be
possible to situate the active regions of the respective TFT
devices thereon.
[0056] FIG. 8A shows an illustration of the first and second
irradiated, re-solidified and crystallized areas 510 and 520
possibly corresponding to the first and second areas 310, 320 of
FIGS. 4D and/or the adjacent portions 462 of the area 460 of FIG.
6D. In particular, FIG. 8A shows that the entire TFT devices 610,
620 can be situated within the respective uniform small-graned
regions 515, 525 of the areas 510, 520. The first TFT device 610
situated in the small-grained region 515 of the area 510 includes a
gate 612, a drain 614, a source 616 and an active region 618, all
of which are provided away from the laterally-grown region 518.
Similarly, for the second TFT device 610, its gate 622, drain 624,
source 626, and especially active region 628 are also situated that
they do not overlap the respective laterally-grown region 528 of
the area 520.
[0057] FIG. 8B shows an illustration of the first and second
irradiated, re-solidified and crystallized areas 510 and 520 also
possibly corresponding to the adjacent portions 462 of the area 460
of FIG. 6D with the respective TFT devices 610', 620' provided
thereon. In this exemplary embodiment, only respective active
regions 618', 628' of the areas 510, 520 are provided within the
respective uniform small-grained regions 515, 525 of the areas 510,
520, while other portions of the TFT devices 610', 620' are
situated on the respective laterally-grown regions 518, 528 of the
areas 510, 520. In particular, the first TFT device 610' includes
an active region 618' which entirely situated in the small-grained
region 515 of the area 510, while a gate 612', a drain 614' and a
source 616' of this TFT device 610' overlap the laterally-grown
region 518. Also, for the second TFT device 610', an active region
628' thereof is entirely situated within the respective
small-grained region 525 of the area 520, while a gate 622', a
drain 624' and a source 626' of the second TFT device 620' are
provided directly on the respective laterally-grown regions 528 of
the area 520. Also, the gate 622', is provided on a border region
500 between the small-grained region 515 of the area 510 and the
small-grained region 525 of the area 520. It should be understood
that any one of the gate 612, 612', 622, 622', drain 614, 614',
624, 624' and source 616, 616', 626, 626' can be provided on the
laterally-grown regions 518, 528 and the border region 500. In
addition, according to still another embodiment of the present
invention, it is possible to situate a small portion of the active
regions 618', 628' of the respective TFT devices 610', 620' on the
border region 500 or the laterally-grown regions 518, 528, while
still having the major portions of these active regions 618', 628'
provided within the small-grained regions 515, 525.
[0058] FIG. 9 show a flow diagram representing a first exemplary
processing procedure of the present invention under at least a
partial control of a computing arrangement of FIG. 1A which uses
the techniques of the present invention of FIGS. 4A-4F and 6A-6D.
In step 1000, the hardware components of the system of FIG. 1A,
such as the beam source 110, the energy beam modulator 120, and the
beam attenuator and shutter 130 are first initialized at least in
part by the computing arrangement 100. The sample 170 is loaded
onto the sample translation stage 180 in step 1005. It should be
noted that such loading may be performed either manually or
automatically using known sample loading apparatus under the
control of the computing arrangement 100. Next, the sample
translation stage 180 is moved, preferably under the control of the
computing arrangement 100, to an initial position in step 1010.
Various other optical components of the system are adjusted and/or
aligned either manually or under the control of the computing
arrangement 100 for a proper focus and alignment in step 1015, if
necessary. In step 1020, the irradiation/laser beam 111 is
stabilized at a predetermined pulse energy level, pulse duration
and repetition rate. In step 1024, it is preferably determined
whether each beam pulse 164 has sufficient energy to fully melt the
irradiated portions of the semiconductor thin film 175 without
over-melting them. If that is not the case, the attenuation of the
beam 111 is adjusted by the beams source 110 under the control of
the computing arrangement 100 in step 1025, and step 1024 is
executed again to determine if the there is sufficient energy to
melt the portions of the semiconductor thin film.
[0059] In step 1027, the sample 170 is positioned to point the beam
pulse 164 to impinge the first column of the semiconductor thin
film. Then, in step 1030, the portions of the semiconductor thin
film are irradiated and filly melted throughout their entire
thickness using a masked intensity pattern or a shaped beam pulse
(e.g., using the mask 150 or merely shaping the beam). Thereafter,
the irradiated portions of the semiconductor thin film are allowed
to solidify and crystallize such that the certain areas of the
solidified portions have been nucleated and include uniform
material therein so as to allow at least the active regions of the
TFT devices to be placed entirely therein. In step 1035, it is
determined whether the irradiation for the current conceptual
column by the beam pulse has been completed. If no, in step 1045,
the sample is continued to be irradiated with the next beam pulse
164. However, if in step 1035, it is determined that the
irradiation and crystallization of the current conceptual column is
completed, then it is determined in step 1045 whether there are any
further conceptual columns of the sample 170 to be processed. If
so, the process continues to step 1050 in which the sample 170 is
translated to that the beam pulse 164 is pointed to the next
conceptual column to be processed according to the present
invention. Otherwise, in step 1055, the exemplary processing has
been completed for the sample 170, and the hardware components and
the beam 111 of the system shown in FIG. 1A can be shut off, and
the process is terminated.
[0060] FIG. 10 shows a flow diagram representing a second exemplary
processing procedure of the present invention under at least a
partial control of a computing arrangement of FIG. 1A using the
techniques of the present invention of FIGS. 4A-4F and 6A-6D, in
which it is preferable to irradiate the sample 170 based on
preassigned locations on the semiconductor thin film 175. Steps
1100-1120 of this exemplary procedure are substantially the same as
the steps 1000-1020 of the procedure of FIG. 9, and thus shall not
be described herein in further detail. In step 1024, however, it is
determined whether each beam 111 has enough energy to irradiate at
least portions of the semiconductor thin film 175 such that the
irradiated portion crystallize. If not, in step 1125, the
attenuation for the beam pulse is adjusted, and the energy fluence
is verified again. Upon the verification of the energy fluence of
the beam pulse, the sample is moved to impinge a first column of
the sample 170.
[0061] Then, in step 1130, the resultant beam 149 is passed through
the mask 159 to shape the beam pulse, and shape the edge portions
of the resultant pulse. Then, the sample 170 is continuously
translated along the current column in step 1135. In step 1140,
during the translation of the sample 170, the portions of the
semiconductor thin film 175 are irradiated, and fully melted
throughout their entire thickness, e.g., using a masked intensity
pattern beam pulse to allow the irradiated portions to be
crystallized. This irradiation of the portions of the semiconductor
thin film 175 can be performed when the beam pulses 164 reach
particular locations on the sample 170, which are pre-assigned by
the computing arrangement 100 and stored in the storage device
thereof. Thus, the beam source 110 can be fired upon the sample 170
reaching these locations with respect to the beam pulses 164.
Thereafter, the irradiated portions of the semiconductor thin film
175 are allowed to solidify and crystallize such that the certain
areas of the solidified portions have been nucleated, and include
the uniforn material therein so as to allow the active regions of
the TFT devices to be placed thereon. Such processing is continued
until the end of the current conceptual column on the semiconductor
thin film 175 (e.g., the edge of the sample 170) is reached. In
step 1145, it is determined whether there are any further
conceptual columns of the sample 170 are to be processed. If so,
the process continues to step 1150 in which the sample is
translated so that the beam pulse 164 is pointed to the next
conceptual column to be processed according to the present
invention. Otherwise, in step 1155 is performed, which is
substantially the same as that of step 1055 of FIG. 9.
[0062] The foregoing merely illustrates the principles of the
invention. Various modifications and alterations to the described
embodiments will be apparent to those sldlled in the art in view of
the teachings herein. For example, while the above embodiment has
been described with respect to at least partial lateral
solidification and crystalization of the semiconductor thin film,
it may apply to other materials processing techniques, such as
micro-machining, photo-ablation, and micro-patterning techniques,
including those described in International patent application no.
PCT/US01/12799 and U.S. patent application Ser. Nos. 09/390,535,
09/390,537 and 09/526,585, the entire disclosures of which are
incorporated herein by reference. The various mask patterns and
intensity beam patterns described in the above-referenced patent
application can also be utilized with the process and system of the
present invention. It should also be understood that while the
systems and processes described above are directed for processing,
e.g., semiconductor thin films, these techniques and systems can
also be used to process other films, including metal thin films,
etc.
[0063] It will thus be appreciated that those skilled in the art
will be able to devise numerous systems and methods which, although
not explicitly shown or described herein, embody the principles of
the invention and are thus within the spirit and scope of the
present invention.
* * * * *